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Dividers & Compasses

Beam Compasses

Mechanical and architectural drawings have sometimes required circles with diameters of several feet instead of the several inches possible with a standard drawing compass. A beam compass was usually sold with just the points, which the user attached to the ends of a metal rod or wooden slat the length of the desired radius of the circle. One end was held in place, and the other end was pivoted around that end, maintaining contact with the paper. The patent model in the collection is a beam compass.

This metal, brass, and ivory U.S. patent model is mounted in a square wooden frame that is painted gold. The trammels are on a 3-1/4" beam that consists of two metal pins and one metal screw. One trammel has a needle point and an ivory handle. The other has an adjustable pen point. Nuts inside the trammels around the screw on the beam set the positions of the trammels. The instrument is supposed to draw lines, circles, concentric circles, and spirals.

Three paper tags are attached to the frame with a red ribbon. The first tag is marked: 1873 (/) M. Toulmin (/) Beam Drafting Compass (/) Received June 5 (/) Passed Aug 5./7. The second tag is marked: 142,823 (/) 3 (/) M. Toulmin (/) Beam Compasses (/) Patented SEP 16 1873 (/) Dividers 1873. A printed picture of the instrument and a summary of the patent application are pasted to the back of this tag. The third tag is marked: (2–225.) (/) No. 142,823. (/) M. Toulmin (/) Beam Compasses (/) Patented Sept. 16th (/) Dividers 1873. This model was found in the Smithsonian, probably during refurbishing of the textile exhibits between 1953 and 1964.

The patentee was probably Joshua Morton S. Toulmin (1823–1896), who was born in Alabama to English immigrants. He was a cotton broker in Mobile in the 1850s and then moved to New Orleans, where he received four patents between 1872 and 1874, including the 1873 patent for this object and "Improvement in Marine Camels" (no. 125,352, issued April 2, 1872). He then became a patent agent in Washington, D.C., and received several more patents himself between 1876 and 1887. He then moved to Baltimore, where he established the short-lived Toulmin Electric Railway Gate Company in 1886 and received more patents between 1887 and 1890, including "Pneumatic Street Car Propulsion" (no. 440,666, issued November 18, 1890). He held a total of about 15 patents for a variety of mechanical and mercantile devices, but this beam compass was apparently never manufactured commercially. Toulmin's son, Harry Aubrey Toulmin (1858–1942), was the highly successful attorney for the Wright Brothers of Dayton, Ohio.